Rev.
354 Adv. Mater. Sci. 33 (2013) 354-359
J. Zhou, Z. Jia, H. Liu and M. Wang
A STUDY ON SIMULATION OF DEFORMATION DURING
ROLL-FORGING PROCESS USING SYSTEM OF SPECIAL
SHAPED AND HAT GROOVE
Jie Zhou, Zhi Jia, Hao Liu and Menghan Wang
College of Material Science and Engineering, Chongqing University, Chongqing 400044, PR China
Received: October 17, 2011
Abstract. The parameters of groove are important in designing roll-forging mould. In this paper,
a kind of special shaped groove is presented to replace the usual rectangular groove, it can
improve the uniformity of material distribution, and decrease loading. Three-dimensional rigidplastic FEM has been used to simulate the deformation process of pass rolling, and the effect of
the system of special shaped and hat groove during deformation of billet is researched. This
paper analyzes the velocity field of material flow, stress-strain field, the characteristics of the
temperature field, the dynamic evolvement process as well as the force-time curve of mould and
mould damage. Application shows that the system of special shaped and hat groove can improve
the uniformity of materials distribution and increase broadening quantity of spring plates in the
process of automobile front-axle roll-forging.
1. INTRODUCTION
Roll forging is a process for reducing the cross-sectional area of heated bars or billets by passing them
between two driven rolls that rotate in opposite directions and have one or more matching grooves
each roll [1]. During roll-forging process, a part of
material flows along the axial direction to increase
length of billet; the other part of material flows along
the radial direction to increase width of billet. roll
forging has remarkable advantages such as high
productivity, high utilization rate of material, good
labor condition, simple equipment structure, long
life of the rolling dies and so on [2]. There are two
factors affecting the quality of products, one is the
material distribution of billet in axial direction; the
other is the spread of billet in the forming process.
To improve the uniformity of material distribution
in the performing procedure, a kind of special shaped
groove is presented, and a numerical value matrix
of the special shaped and hat groove roll-forging
process is set up. Besides, the author analyzed
the dynamic evolvement process of the mold
damage as well as the affect of hat groove and
special shaped groove.
2. FEM MODEL
2.1. Special shaped groove design
In traditional design, rectangular groove was used
to distribute material in roll forging process, and put
pressure on the top of the billet. This groove will
reduce uniformity of distribute material, cause
uneven wear in mould, thus affects the subsequent
process [3]. The cross-section shape of rectangular
groove is shown in Fig. 1a.
A kind of special shaped groove is presented to
resolve the problems above in this paper. As a
combination of oval groove and diamond groove, it
puts pressure on the side of billet, and keeps clear
of the top of billet. This structure of groove increases
Corresponding author: Zhi Jia, e-mail: [email protected]
f
1M JWL M@]Mb3 W][3X ;]
M
A study on simulation of deformation during roll-forging process using system of special...
355
(a)
(a)
(b)
(c)
Fig. 1. Cross-section shape of grooves for simulate:
(a) Rectangular groove; (b) Special shaped groove;
(c) Hat groove.
the contact area between die and billet, avoids the
heterogeneous deformation, and increases the
stability of billet. The range of the slope ( 2) and
slope (
R,)e
d )eH
(IA L[
X
L]
R
XW JY
of the special shaped groove is shown in Fig. 1b.
2.2. FEM model
The system of special shaped and hat groove used
for simulation is shown in Figs. 1b and 1c. The
parameters in simulation are shown in Table 1. The
billet is pre-formed in this kind of special shaped
groove pass and then enters the hat groove pass
JO
][[
X]
J]
R
WP- eJ[
X WMR
] JaR 6R
P
X ]
FEM model of the process.
(b)
Fig. 2. Finite element model of roll forging: (a) First
rolling pass; (b) Second rolling pass.
W] U
XY J XO J]P[
XX R-e U
XY
R
eJWM]
[
JW R
]
R
XW[
X WMLX[
W [[
JMR r) is 30 mm.
3.1. Stress and strain field
Fig. 3 shows the stress and strain distribution in
deforming zone of billet of special shaped groove. It
is uniform distribution in the cross-section. The
maximal stress and strain distribute in the contact
area of billet and mold. Besides, the stress and strain
are brought down with the reduction of distance from
the contact area. The effective strain is 0.034 in the
center of blank and non-contact area, which
Table1. Parameters in simulation.
3. THE EFFECT OF SPECIAL
SHAPED AND HAT GROOVE
SYSTEM ON THE FORMING
The rolling forging process of system of special
shaped and hat groove is researched, the variation
process of the stress-strain field, velocity field and
temperature field is discussed, and the mechanical
parameters and injury in the forming is analyzed
Parameters
Value
Diameter of billet
Length of billet
Friction coefficient
Angel velocity
Material
Initial temperature
140 mm
500 mm
0.5
1.8 rad/s
AISI 1045
1100 e
C
356
J. Zhou, Z. Jia, H. Liu and M. Wang
(a)
(a)
(b)
(b)
Fig. 3. Stress and strain field in special shaped
groove pass rolling during roll-forging: (a) Stress; (b)
Strain.
indicates that the deformation is small in the major
area of the special shaped groove.
Fig. 4 shows the stress and strain distribution in
deforming zone of billet of hat groove. The stress
and strain distributes symmetrically on the cross
section of hat groove rolled piece. The value of strain
is the largest on the circular arc transition, and
reduces towards the center of billet. The stress
reduces from bottom to top in the deformed area,
and the maximal stress is on the center of bottom.
The equivalent stress in the outer layer of billet is
higher than that of the center. And it is the lowest
on the top.
3.2. The velocity field in the roll
forging process
Fig. 5a shows the velocity field distribution of billet
in the deforming area of hat groove. Fig. 5b shows
the velocity field distribution in the Y-direction. The
billet extends in the axial direction and spreads in
radial direction. In different nodes, the flow velocity
is different. From Fig. 5a, it can be seen that the
Fig. 4. Stress and strain field in hat groove pass
rolling during roll-forging: (a) Stress; (b) Strain.
flow velocity reaches its maximum in the forward
slip zone, and gradually reduces toward the
backward slip zone. In the y-o-z cross section, the
flow velocity is the largest in the circular arc transition,
and gradually reduces toward the center of blank
and the edge. From Fig. 5b, it can be seen that Ydirection flow velocity is the highest on the edge of
blank, and gradually reduces toward the center of
blank [5].
3.3. The influence of mold in rollforging process
Fig. 6 shows the wear depth distribution of special
shaped and hat groove roll-forging mold. The tool
wear focuses on the groove lateral in special-shaped
groove roll-forging mold, because the pressure
exerted by groove side forces the billet to deform,
JWMX] [YJ[
] MXWg
] a[
]Y[ [ ]
X] R
U
U]
The maximum wear depth is 0.00519. The wear depth
of hat groove roll forging mold focuses on the
transitional rounding, and the farther to the center,
the wear depth is lower.
A study on simulation of deformation during roll-forging process using system of special...
357
(a)
(b)
Fig. 5. Velocity field in hat groove pass rolling during roll-forging; (a) Total velocity (b) Y direction velocity.
(a)
(b)
Fig. 6. The wear depth distribution of special shaped and hat groove roll-forging mold; (a) Special shaped
groove mold (b) Hat groove mold.
358
J. Zhou, Z. Jia, H. Liu and M. Wang
Fig. 7. Shapes of the workpiece in rectangular-hat groove pass rolling during roll-forging: (a) in rectangular
groove: (b) in hat groove.
Fig. 8. Shapes of the workpiece in special shaped and hat groove pass rolling during roll-forging: (a) in
special shaped groove: (b) in hat groove.
4. EXPERIMENT
Front axle is an important component of automobile
that bears heavy loads [6]. Process of automobile
front-axle roll-forging is carried out to validate the
simulation results, and the comparison of forming
effect between the system of rectangular-hat groove
and the system of special-shaped and hat groove.
All experiments use lead rods. Fig. 7 shows the
shapes of workpiece under system of rectangularhat groove at the end of two procedures respectively.
Fig. 8 shows the shapes of workpiece under system
of special-shaped and hat groove. From the
comparison, it can be found that the simulation is
in good agreement with the experiment. When the
system of rectangular-hat groove is used for roll
forging mould, the front-axle billet has a fan-shaped
spring plates. When the system of special-shaped
and hat groove is used for roll forging mould, the fan
shaped structure at spring plates is replaced by
rectangular structure, and the shape of spring plates
becomes consistent with a larger spread amount.
5. CONCLUSIONS
The deformation behavior in roll-forging process under
different shaped grooves has been studied. Some
conclusions can be drawn out as follows:
(1) In this paper, a special shaped and hat groove is
proposed, which could improve uniformity of material
distribution effectively due to the constraint offered
by lateral pressure.
(2) In the roll-forging process of automobile frontaxle, the system of special-shaped and hat groove
can improve uniformity of materials distribution
effectively, and increase the spread quantity of spring
plates, and reduce loading.
A study on simulation of deformation during roll-forging process using system of special...
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359
[4]Y.F. Xia, Jie Zhou, Zhi Jia, A Precision
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201010042025.X.
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